1. Field of the Invention
The invention relates to a drive device, especially for moving and turning the slats of a blind in a runner, wherein the rotational movement of a drive wheel can be alternately transmitted to a turning drive means effecting the turning movement of the slats by means of a change gear and to a transport drive means effecting the movement of the slats in the runner, wherein the change gear comprises a drive tube, which can be driven in both directions of rotation via the drive wheel, and a shaped reversing shaft extending coaxially to the drive tube, which can be rotated by a certain angle relative to one another, and wherein the drive tube is connected to a drive for the transport drive means to rotate therewith via locking members arranged offset in the longitudinal and peripheral direction over its periphery in dependence on the angular position of the reversing shaft with respect to the drive tube in one shifting position and is connected to a drive for the turning drive means to rotate therewith in another shifting position.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98.
Such a drive device is known from DE-A 2 223 610. In this arrangement, a drive wheel, which can be operated by a cord or chain pull, rotates a drive tube with which it is engaged. In the wall of this drive tube radially movable locking members are provided, offset with respect to one another both in the peripheral and in the longitudinal direction, which, depending on the position of a shaped shaft, which can also be rotated by the drive wheel via a driving device within the drive tube, are held in engagement with one of two toothed sleeves arranged behind one another on the drive tube or can be moved out of the area of engagement with the respective other toothed sleeve. A turning shaft effecting the turning of the slats can be driven via one of the two toothed sleeves and a transport spindle effecting the movement of the slats can be driven via the other one. By changing the direction of rotation at the drive wheel, the blind can thus be pulled open and shut by means of the longitudinal displacement of the slats, on the one hand, and, on the other hand, brought into a position allowing more or less light to pass in a state in which the blind is pulled shut wholly or partially, that is into a wholly or only partially closing position, by turning or rotating the slats around their longitudinal axis.
Since the blind cannot be pulled open, i.e. the slats cannot be pushed together not, without interference when the slats are in their completely closing turning position because they then abut one another, a further development of the said gear ensures that each directional change at the drive wheel is followed by a turning or rotating of the slats and the turning shaft is decoupled at the gear and the drive is shifted to the transport spindle only after a certain angle of rotation has been reached which goes beyond the closing of the slats.
Shifting from one shifting position to the other one is effected by a limited relative rotation between the drive tube and the shaped shaft and this relative rotation is made possible by a toothed disk which is permanently joined to the shaped shaft and has mirror-inverted locking teeth on both sides, with a driving and a sliding edge, which, on one side, can lock in to a notched disk permanently joined to the drive wheel and, on the other side, into a second notched disk permanently joined to the drive tube, wherein the drive tube, after the locking, is entrained by driving tabs which protrude into arc-shaped slots of the drive wheel and allow a relative rotation of the drive wheel with respect to the drive tube. The individual parts of the mechanical shifting arrangement are exposed to high torques and surface pressures during the operation which can lead to premature wear and also to disturbances due to jamming. To ensure as trouble-free operation of these drive devices as possible, it is necessary to maintain very small production tolerances in the parts of the mechanical shifting arrangement, which makes production more expensive.
Moreover, it has been found in practical application that the shifting process which is subdivided into a number of part-processes, and which requires a brief turning back and forward at the drive wheel with each shifting process for example, is considered to be too complicated by most users. Because of this complicated shifting process, this drive device is also not very suitable for an electric motor drive.
In DE 2 737 416 C2 and DE 25 54 991 B2, a gear is described in which the shaped shaft described above is held in a central rest position with respect to the drive tube, or always returned to this position in which the locking members, which can be radially moved in the drive tube, are held in engagement with the toothed sleeve via which the turning shaft is driven, by a restoring spring so that, when the drive wheel is turned, initially it is always the turning shaft which is first driven and, as a consequence, the slats are rotated, i.e. turned, around their longitudinal axis. At the transport spindle, a free run, limited in both directions by a roller and by a stop, is provided which allows a next toothed sleeve meshing with the second tooth sleeve driven by the drive tube to rotate loosely on the transport spindle up to the end of the free run. At the end of the free run, a non-positive connection is obtained between the transport spindle and the toothed sleeve which rotates loosely on the former up until then, so that the transport spindle is now entrained in the rotation. Due to the higher torque to be transmitted by the drive tube during this process, the shaped shaft is pivoted against the force of the restoring spring inside the drive tube and relative to the latter by a driving device, to such an extent that, as a result, the toothed sleeve driving the turning shaft is decoupled.
The transport spindle which is now coupled on alone effects the movement of the slats in the runner. The angle at which the slats are positioned with respect to the running direction here always corresponds to one of the end turning positions of the slats and is determined by the length of the free run; it is approx. 150xc2x0 in both directions. To ensure the shifting from turning to moving, a braking device which can be adjusted by means of an adjusting screw is also provided on the free-run shaft, by means of which the higher torque required for the shifting can be increased again.
While the drive wheel can also be driven by electric motor instead of with the aid of a cord or chain pull in this case, the shifting from drive to the turning shaft to drive to the transport spindle is done purely mechanically. Because of the large torques occurring during this process, individual parts, especially of the limited free run in its end positions, are subject to high loading. The forces and surface pressure occurring during this process can lead to wear and also to jamming as a consequence of production tolerances. In addition, it is no longer possible subsequently to change or adapt the number of idle rotations between the toothed sleeve and the transport spindle driven by it.
It has also been found that, in spite of the angular position of the slats of 150xc2x0 with respect to the running direction during the movement of the slats, the latter tend to become hooked together, especially if they are loosely connected to one another by beaded strings at their freely suspended ends or if the runner is attached to an inclined surface, for example a roof slope. The slats also require a relatively large amount of space on the side, e.g. of a window, in the pushed-together state, that is to say when the blind is open, with an angular position of approx. 150xc2x0.
It is the object of the invention to create a drive device of the type initially mentioned, the change gear of which is suitable for an electric motor drive and in which too high a load on individual parts of the change gear, and this their premature wear, is avoided. Fewer individual parts which have to be manufactured with high precision should be required and thus the production costs lowered. It should be possible for the slats of a blind to move in a trouble-free manner, especially without becoming hooked into each other and impeding one another, along the runner for pulling the blind open and shut and, in addition, to rotate them continuously in both directions between a wholly and an only partially closing rotating or turning position in each position of movement of the slats in order to regulate by this means the incidence of light. The shifting process from turning to moving and conversely should be simplified in such a manner that it, too, and not only the movement itself, can be effected by electrical or electronic means so that the device also becomes bus-capable for the central operation and control of a number of blinds individually or in groups. Trouble-free operation should be guaranteed.
According to the invention, this is achieved by the fact that the reversing shaft is connected to a magnetizable brake disk which faces a stationary electromagnet to rotate therewith and that when current flows through the induction coil of the electromagnet, the brake disk is pulled against the electromagnet 25 and thus the reversing shaft is stopped against rotation and the drive tube can be rotated by an angle corresponding to the two shifting positions relative to the reversing shaft whilst when the induction coil of the electromagnet is without current, the reversing shaft and brake disk can be rotated together with the drive tube.
In this manner, the shifting process based on a relative rotation between drive tube and reversing shaft can be carried out by an electrical signal. The shifting process puts much less load on the individual mechanical parts than in known devices so that premature wear and also operational disturbances, e.g. due to jamming are avoided. The slats of the blind can also be rotated about their longitudinal axis in any intermediate moving position and not only, as known, when the blind is completely closed, and thus the incidence of light can be regulated. The drive device is distinguished by a compact space-saving type of construction and the production costs are considerably reduced.
In accordance with a preferred embodiment, the drive tube and the reversing shaft and brake disk are held in a center position corresponding to one shifting position of the change gear with respect to one another by the force of a restoring spring where the induction coil of the electromagnet is without current, and can be jointly rotated, but when current flows through the induction coil of the electromagnet, the drive tube is rotated by the angle corresponding to the other shifting position relative to the reversing shaft against the force of the restoring spring. The change gear of the drive device according to the invention can thus be advantageously shifted in both directions.
As an alternative, the drive tube and the reversing shaft can be held in the one shifting position with respect to one another, in which they can be jointly rotated, when current flows through the induction coil of the electromagnet; when the induction coil of the electromagnet is without current, the drive tube can then be rotated by an angle corresponding to the other shifting position of the change gear with respect to the reversing shaft by means of a braking force, e.g. of a brake spring.
The exciter current for the electromagnet is preferably switched on and off in dependence on the angular position of the slats of the blind with respect to the direction of movement. It is then possible to avoid the slats becoming hooked together or otherwise impedeing one another by bringing the slats into a certain angular position, preferably 90xc2x0 with respect to the direction of movement before they are moved.
The exciter current for the electromagnet can be switched on and off by means of an electronic circuit in dependence on time or analog values or number of pulses.
According to a preferred embodiment of the invention, when the drive device is operated the position of movement of the slats in the runner and their angular position with respect to the direction of movement can be electronically detected and the exciter circuit for the electromagnet can be closed or interrupted in dependence on these two positions of the slats.
The change gear can preferably be held in the shifting position driving the transport drive means only at a defined angular position of the slats of approx. 90xc2x0 with respect to the direction of movement, or brought into this shifting position. In this angular position of the slats, they cannot impede each other during the movement in the runner, especially also on a slope.
In the case of an angular position of the slats deviating from approx. 90xc2x0 with respect to the direction of movement, first the change gear is brought into the shifting position driving the turning drive means when the drive device is operated.
It is only in the end position of movement of the slats, which corresponds to the completely opened blind, that the change gear cannot be brought into the shifting position driving the turning drive means because in this case they are automatically located in the correct and also space-saving angular position of approx. 90xc2x0 with respect to the direction of movement for a movement in the reverse direction at the end of a preceding moving process; this ensures that the slats, on the one hand, can be rotated, that is to say turned, about their axis, both with the blind pulled shut and also in any intermediate position of movement, for regulating the incidence of light, and, on the other hand, with the blind completely opened when the slats are hanging closely next to one another in the angular position of 90xc2x0, their rotation and thus interference can be avoided.
Since the moving of the slats normally requires a longer period of time than the turning, it is considered to be advantageous if, where the induction coil of the electromagnet is without current, the shifting position assumed by the change gear is the one in which the transport drive means for moving the slats in the runner can be driven, and the shifting position assumed by the change gear when current flows through the induction coil of the electromagnet is the one in which the turning drive means for rotating or, respectively, turning the slats can be driven.
Due to the fact that the circuit of the change gear is electronically controlled, together with the electric motor drive of the drive device, the latter is also provided with bus capability. A number of motors, that is to say a number of blinds, can be operated and controlled centrally via a bus system individually or in groups.
The device is preferably driven with the aid of synchronous motors; these have the advantage that, in contrast to, for example, DC motors, they always run evenly. This attains special significance in the case of blinds, the slats of which are carried in a runner at both ends. Such a two-sided guidance can be of advantage, for example in the case of very long slats and/or very windy installations or could also be required, for example, in the case of roof windows or in the case of horizontally arranged slats.